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Publication > Issue > Articles

Refining turns sour

Summary

Refiners in the Arabian Gulf are replacing sour crude exports with finished products for export that meet the highest standards for clean fuels. As a result, quantities of sulphur that were previously exported as part of crude shipments are increasingly recovered in the Gulf region where the oil originates.

Abstract

Oil industry interest in refining has revived in the past few years in response to rising oil consumption worldwide, especially in China. Capacity bottlenecks have forced prices for refined products to high levels even at a time of relative oil plenty. The Middle East in particular has traditionally been an exporter of raw crude and does not have the large refinery capacity that the region’s large oil reserves might suggest. It is hoped by many in the oil market that in closing this gap between reserves and refining capacity, some of the instability now characteristic of the market may also be eased.

Such is the current pace of expansion in the region that refining capacity is projected to increase by 60 % over the next few years, overtaking Russia, yet even this may not be enough. The Abu Dhabi-based Emirates Centre for Strategic Studies and Research has projected that the Gulf States need to invest $523bn over the next 25 years to meet the steady growth in global oil demand and $99bn to expand their refining capacity from around 6.0m bbl/day in 2002 to 10m bbl/day in 2010 and 15.6m bbl/day by 2030.

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Sulphur in agriculture - later than we think?

Summary

Agronomists in Europe and North America have been arguing for nearly two decades that farmers must restore nutrient sulphur levels in the soil to levels lost through tougher environmental regulations, while elsewhere in the world, the intensification of agriculture has similarly highlighted increasing levels of sulphur deficiencies. Mark Evans, Editor of Fertilizer International, assesses the prospects for enhanced sales of sulphur through various formulations, including sulphur-coated fertilizers.

Abstract

There is a market out there, but its size, scope and prospects remain difficult to measure. While sulphur has lately been identified as the Fourth Major Nutrient (after N, P and K) and is needed by every crop, a match of demand and supply of sulphur for agricultural applications has yet to be adequately achieved. The problems in forging an effective plant nutrient sulphur market mech­anism lie on both the demand and supply sides of the equation.

Getting farmers to recognise their need to apply adequate levels of sulphur has been the major goal of agronomists and other advocates of plant nutrient sulphur (PNS). Sulphur is recognised as a secondary nutrient, one of 16 essential plant nutrients, and plays three key roles in agriculture:

  • As a soil amendment for pH adjustment
  • As a plant nutrient
  • As a fungicide.

Sulphur is absorbed by plants in amounts comparable to P, for which the worldwide demand is around 35 million t/a P2O5. How­ever, according to some industry analysts, only about 10-12 million t/a of sulphur is presently applied as sulphur fertilizer, a large proportion involuntarily in the form of the “free sulphur” incorporated in such fertilizers as single superphosphate (SSP) or ammonium sulphate (AS).

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Handling sulphur plant vent gases

Summary

Most sulphur recovery facilities route the sulphur pit vent to the incinerator, where the H2S in the stream is oxidised to SO2, directly impacting SO2 emissions. For facilities with tight emission restrictions and/or high recovery efficiency requirements, routing the pit vent to the SRU thermal section, tail gas RGG or caustic scrubbing may provide the best solution.

Abstract

Environmental regulatory agencies of many countries continue to stipulate more stringent standards for sulphur emissions from oil, gas and chemical processing facilities. However, with the overall sulphur recovery efficiency of sulphur recovery units with tail gas treating commonly exceeding 99.9 %, attention has turned to other sources of sulphur emissions in refineries and gas plants and there has been increasing interest in the pursuit of low-emission options for safe disposal of vent streams from sulphur pits, sulphur storage tanks and sulphur loading facilities.

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CrystaSulf revisited

Summary

Following the successful operation of the first commercial CrystaSulf unit at the Norsea gas terminal in Emden, northwest Germany, CrystaSulf technology has been selected as the sulphur control technology for the Clean Coal project power plant to be built at Orlando, Florida. In this plant, CrystaSulf will desulphurise the 360,000 Nm3 / h syngas stream at 30 bar and yield up to 10 t/d of sulphur cake product. Dennis Dalrymple of CrystaTech reports on the latest developments.

Abstract

The CrystaSulf process effectively treats gas containing too much hydrogen sulphide (H2S) for a scavenger system, but too little H2S for an amine/Claus. The CrystaSulf process removes H2S from sour gas and converts it to elemental sulphur via the liquid-phase modified Claus reaction:

2H2S + SO2 ® 3/xSx + 2H2O

Since it is not adversely affected by common gas contaminants, CrystaSulf is effective on gas streams with contaminants such as carbon dioxide, oxygen, mercaptans and slugs of liquid hydrocarbons. This process was described in the September-October 2004 issue of Sulphur.

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Sulphur condensation in Claus catalysts

Summary

Catalyst deactivation by pore plugging with liquid sulphur may decrease the effectiveness of a Claus unit. L.V. Morgun, O.E. Filatova and N.V. Motin of VNIIGAZ discuss how this effect can be avoided, and what temperature regime should be chosen.

Abstract

The effectiveness of the Claus process depends largely on two conditions: keeping the proper ratio of acid gas and air, and the activity of the catalyst. Modern alumina catalysts provide for almost equilibrium conversion of sulphur compounds, however, over time the activity of the catalyst deteriorates as a result of the following mechanisms:

  • surface area decrease due to thermal and hydrothermal destruction;
  • catalyst surface sulphation;
  • coke formation at the catalyst surface;
  • pore plugging by liquid sulphur.

The deactivation of Claus catalysts has been extensively researched, but has focused mainly on the first three mechanisms. Pore plugging by liquid sulphur has been described only in one article known to the authors. Perhaps this type of deactivation is considered less dangerous, because it does not physically damage the catalyst.

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Versatility of liquid redox processing

Summary

Liquid redox systems are extremely versatile for small-scale sulphur recovery. Sulphur discusses its flexibility for refinery sulphur management and reports on a new use for Lo-Cat® sulphur to produce an environmentally-friendly sulphuric acid that farmers can use to clean scale and algae from their irrigation equipment.

Abstract

With the installation of more and more desulphurisation processes to meet ultra low sulphur specifications for gasoline and diesel in conjunction with ever increasing pressure from environmental agencies to reduce sulphur emissions, refiners are faced with the challenge of what to do with the additional H2S being generated. In some cases, there is sufficient spare capacity in the existing amine and Claus units to process the additional load. In other cases, the existing Claus unit(s) can be updated with oxygen enrichment technology to handle the additional load. Alternatively, new sulphur recovery systems may be required to handle the incremental load.

Another approach to this challenge, which is often overlooked, is the addition of liquid redox processing. Due to its excellent versatility, sulphur recovery via liquid redox processing can be employed to treat any type of sour gas streams. In a refinery this means that liquid redox technology can be use to treat sour, gaseous hydrocarbon-based streams directly or acid gas streams from amine units, or sour water stripper gas or even Claus tail gas streams. By integrating liquid redox processing into the overall refinery sulphur recovery program, refiners may be able to easily accommodate the additional sulphur recovery burden imposed by the production of ultra low sulphur fuels.

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New sulphuric acid producing plant

Summary

From sulphur burning to smelter gas capture, Sulphur's annual survey covers recent and planned construction projects for sulphuric acid production.

Abstract

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